1. Field of the Invention
The present invention relates to a positive electrode for an alkaline battery that can constitute an alkaline battery having a high capacity and exhibiting excellent load characteristics, and an alkaline battery using the positive electrode for an alkaline battery.
2. Description of Related Art
Alkaline batteries using manganese dioxide as a positive electrode active material have been recently used for an increasing number of applications that require charging at a comparatively large electric current value, such as the power source for digital cameras, and there has been a need to improve the load characteristics of alkaline batteries.
Under such circumstances, a technique for improving the load characteristics of alkaline batteries by using spinel-type manganese dioxide (lambda-type manganese dioxide) as a positive electrode active material is proposed, for example, in JP 2007-048737 A and JP 2007-123149 A.
Although alkaline batteries using spinel-type manganese dioxide as a positive electrode active material exhibit improved load characteristics, they suffer from a very low discharge capacity. For this reason, in JP 2007-048737 A and JP 2007-123149 A above, electrolytic manganese dioxide (gamma-type manganese dioxide), which is used in conventional alkaline batteries, is used in combination with spinel-type manganese dioxide, thereby avoiding a decrease in the discharge capacity.
However, the amount of spinel-type manganese dioxide in the positive electrode active material needs to be set very small in order to secure a practically useful discharge capacity by a method using electrolytic manganese dioxide in combination with spinel-type manganese dioxide, and therefore, there is a limit in ensuring the effect provided by use of spinel-type manganese dioxide.